1. How is estimated Average Glucose (eAG) calculated?
The ADAG formula that is used to calculate the eAG from your A1c result is:
28.7 X A1c – 46.7 = eAG
An example of this is an A1c of 6%. The calculation for this would be:
28.7 X 6 – 46.7 = 126 mg/dl
for an estimated average glucose of 126 mg/dl.
What this means is that for every one percent that your A1c goes up, it is equivalent to your average glucose going up by about 29 mg/dl.
^ Back to top
2. Is there a home test for A1c?
Yes. There are FDA-approved tests that can be used at home. If you are interested in learning more, visit the article on
Home Tests and ask your doctor.
^ Back to top
3. Can the A1c test be used to screen for or diagnose diabetes?
This is a question that is currently being explored by the medical community, but the A1c test is not yet recommended for these purposes. The A1c test has the advantages of not requiring a person to be fasting and of giving an estimate of glucose levels for the past couple of months. There are, however, conditions such as
anemia or the presence of
hemoglobin variants that can interfere with the test’s interpretation. And there are currently no established cutoff values to compare A1c test results to in order to use them for
diabetes screening or diagnosis.
^ Back to top
4. Are all A1c tests the same?
Not yet, but great strides have been made in standardizing the A1c test. For more than a decade, a variety of national and international organizations have been working together as part of the National Glycohemoglobin Standardization Program and/or as part of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Included in the recent consensus statement of the ADA, IFCC, European Association for the Study of Diabetes, and the International Diabetes Federation were statements regarding a new way of reporting (see
What does the test result mean?) and a statement recommending that a new improved reference system developed by the IFCC be adopted as the only valid “anchor” for measurement standardization. In the past, A1c tests have used different methods that have measured one or more of the glycated subcomponents of hemoglobin A. The result of this was an A1c test result that could vary significantly depending upon which method was used. The IFCC method measures only hemoglobin A1c.
The process of using the IFCC method will be invisible for people having an A1c test performed. The NGSP is in the process of certifying that manufacturers’ are capable of producing the same results as the IFCC system. Practically, as this is adopted over the next few years, it means that a person would get the same or very similar A1c results regardless of to which laboratory their test was sent.
^ Back to top
